1. Field of the Invention
This invention relates to the field of brakes. Most particularly, this invention relates to a system, method and apparatus for measuring a condition of a brake using sensor-wear material embedded in the brake.
2. Background
Brakes often control the motion of vehicles, particular motor vehicles, such as cars, buses, SUVs, minivans, vans, trucks, and military vehicles. A driver typically applies a brake, such as a brake of a vehicle, by pressing on a brake pedal or pulling a brake lever. When applied, the brake slows down or stops the vehicle by use of friction on a rotating surface.
Motor vehicles generally use one or both of two types of brakes: disc brakes and drum brakes. FIG. 1A shows a typical disc and rotor brake assembly 100 for use with a motor vehicle. The typical disc and rotor brake assembly 100 has a rotor 110 and two disc-brake pads 120 and 130. The disc-brake pad 120 is made up of friction material 122 mounted on a backing pad 124. The disc-brake pad 130 is typically a symmetric counterpart to disc-brake pad 120, also made up of friction material 132 mounted on a backing pad 134. Disc and rotor brake assemblies are often used in automobiles.
Typically, when the brake is applied, (i.e., a driver presses on a brake pedal), a fluid is forced through a series of tubes and hoses to a brake assembly at each wheel of the vehicle. The fluid typically is either air or “brake fluid”. Air is used as the fluid for air brakes, which commonly control the motion of rail cars and heavy trucks. A typical brake fluid is hydraulic oil, which is often used with automobile brakes. In the case of a disc and rotor brake assembly, the action of the fluid causes disc-brake pads 120 and 130 to move toward and then contact the rotor 110. The friction material 122 and 132 on each respective disc-brake pad 120 and 130 contacts the rotor 110 to slow or stop the vehicle via friction.
FIG. 1B shows a cross-sectional view of a typical drum brake assembly 150, consisting of a drum-brake shoe 160 with friction material 162 mounted on a backing pad 164. The drum-brake shoe 160 is mounted inside a drum 170 that rotates with a wheel of the vehicle. When the brake is applied, the action of the fluid pushes the drum-brake shoe 160 toward the surface of the drum 170, and the friction material 162 contacts the drum 170 to slow or stop the vehicle via friction. Drum brake assemblies are often used with air brakes and as automotive emergency brakes.
As brakes typically use friction to slow or stop a vehicle, they are subject to wear. Typically, visual inspection of the brakes determines an amount of “brake wear” or the wear of the friction material of the brake. As brake wear increases, a typical brake may provide audible indicators of wear, such as squeaking or “chirping” sounds. If a brake becomes overheated, due to excessive use or other reasons, the brake may “glaze” when the friction material heats enough to liquefy. When cooled, the formerly liquefied friction material may form a coat or glaze over the brake that reduces the effectiveness of the glazed brake.